Link Grammar

Davy Temperley Daniel Sleator John Lafferty

The Link Grammar Parser is a syntactic parser of English, based on
link grammar, an original theory of English syntax. Given a sentence,
the system assigns to it a syntactic structure, which consists of a
set of labeled links connecting pairs of words. The parser also
produces a "constituent" representation of a sentence (showing noun
phrases, verb phrases, etc.).

We have made the entire system available for download on the web.
The system is written in generic C code, and runs on any platform with
a C compiler. There is an application program interface (API) to make
it easy to incorporate the parser into other applications.

As of December 2004, we are releasing the parser under a new
license; the license allows unrestricted use in commercial
applications, and is also compatible with the GNU GPL (General Public
License). You can view the license here. We
are also releasing version 4.1b, which is identical to version 4.1
(released in 2000) except that the licensing statements reflect the
new license.

The parser has a dictionary of about 60000 word forms. It has
coverage of a wide variety of syntactic constructions, including many
rare and idiomatic ones. The parser is robust; it is able to skip over
portions of the sentence that it cannot understand, and assign some
structure to the rest of the sentence. It is able to handle unknown
vocabulary, and make intelligent guesses from context and spelling
about the syntactic categories of unknown words. It has knowledge of
capitalization, numerical expressions, and a variety of punctuation
symbols.

The parser is now being maintained under the auspices
of the Abiword project. The latest versions include new features
and many improvements. For more information, go to the
Abiword
link grammar page.

Acknowledgements

The research described here was supported by NSF,
ARPA, and the School of Computer Science, at Carnegie
Mellon University. Special thanks to Adam Berger
for developing the post-processing system, and to Dennis Grinberg for
contributions to the null-link system.